The present invention relates to a metal body discriminating apparatus for discriminating a material, a shape, a size, and the like of a metal body such as metal product, metal part, coin, etc. by a magnetic principle.
Hitherto, a case where such a metal body discriminating sensor is used to, for instance, discriminate a coin of an electronic coin detecting apparatus has been know. Such apparatuses have been disclosed in JP-A-59-178592, JP-A-57-98089, JP-B-1-25030, International Publication WO86/00410, U.S. Pat. Nos. 4,462,513, 4,493,411, 4,845,994, and 4,601,380, and the like.
One typical example of such conventional electronic coin detecting apparatuses will be described hereinbelow with reference to FIGS. 30 to 34D. In FIG. 30, a coin 1 which has been put in from a coin input port rolls and moves in the electronic coin detecting apparatus along a guide rail 2 which is inclined to a front side A. The guide rail 2 is formed so as to have width in consideration of a thickness of coin as an object to be detected and is designed so as to adjust a forward inclination angle, to flatten the rolling surface, and the like so that the coin can smoothly roll. The movement in the lateral direction of the coin 1 is restricted by a side wall 3 which is formed perpendicularly to the surface of the guide rail 2 and a side plate (shown by a broken line) 4 which faces the side wall, 3, thereby allowing the coin 1 to roll so as not to be dropped out from the guide rail 2.
The side wall 3 is slightly inclined to the back surface side in a manner such that when the coin 1 rolls along the guide rail 2, the coin 1 always slides with the surface of the side wall 3 by the dead weight of the coin.
Detecting coils 5 and 65 are buried in the side wall 3. A detecting coil 7 is buried in the side plate 4 at a position which faces the detecting coil 5. The detecting coils 5 and 7 are provided in a positional relation such that when the coin 1 passes, it faces almost the central portion. The detecting coil 6 is provided in a positional relation so as to face the peripheral portion of the coin 1.
The detecting coils 5 to 7 correspond to the conventional metal body discriminating sensors. Each of the detecting coils has a structure such that a copper wire 10 is wound around a projecting portion 9 on the inside of a cap-shaped ferrite core (pot core) 8 as shown in FIG. 31. The detecting coils 5 and 6 are buried in the side wall 3 and the side plate 4 so that each projecting portion 9 is directed toward the side of the passage of the coin 1.
Each of the detecting coils 5, 6, and 7 detects the coin 1 by a detecting circuit combined with a bridge circuit as shown in, for instance, FIG. 32. That is, resistors r1 and r2 having predetermined resistance values and an adjusting resistor R1 and an adjusting coil L1 whose values have been preset to proper values are connected to an oscillating circuit 11 of a predetermined frequency. A detecting coil LO (corresponding to the detecting coil 5, 6, or 7) is connected to one side of the bridge circuit, thereby generating a detection signal S from a predetermined output contact.
Thus, as shown in FIG. 33, the detecting coils 5, 6, and 7 driven by the oscillating circuit 11 generate magnetic lines of force (shown by broken lines in the diagram) having predetermined magnetic flux densities on the side of the passage of the coin 1. The bridge circuit is set into an equilibrium state by changes in inductances and impedances of the detecting coils 5, 6, and 7 which are caused due to influences by eddy currents occurring in the coin 1 when the coin 1 transverses in the magnetic lines of force. Thus, the detection signal S indicative of a feature of the coin 1 is generated. The detecting coils 5 and 7 face each other and construct a set of magnetic circuit (corresponding to an inductance LO in FIG. 32), thereby generating magnetic lines of force which perpendicularly transverse the passage of the coin 1. The coin 1 is detected when it passes in the magnetic lines of force. On the other hand, as shown in FIG. 33, the detecting coil 6 generates magnetic lines of force one side of the passage of the coin 1, so that the coin 1 is influenced by the magnetic lines of force from one side.
The coin detecting operation of the apparatus will now be described with reference to FIGS. 34A to 34D. The above diagrams show that when the coin 1 rolls toward the front direction A along the guide rail 2 for a pair of detecting sensors 5 and 7 arranged at predetermined positions for the guide rail 2, the detection signal S which is generated from the detecting circuit changes in accordance with changes in relative positions between the coin 1 and the detecting sensors 5 and 7.
When the coin 1 is away from the above detecting sensors as shown at a certain time point t1, the bridge circuit in FIG. 32 is not in the equilibrium state, so that the detection signal S (refer to FIG. 34B) having the same frequency f and amplitude H as those of the output signal of the oscillator 11 is generated.
As shown at a time point t2, when the front edge portion of the coin 1 approaches between the detecting coils 5 and 7, an eddy current is generated in the approach portion due to an influence by the magnetic lines of force, so that the inductance LO of the bridge circuit changes and the amplitude of the detection signal S changes (refer to FIG. 19c). When the coin 1 further progresses between the detecting coils 5 and 7, a level of eddy current which is generated also gradually increases and the amplitude of the detection signal S also changes in accordance with the change in eddy current.
As shown at a time point t3, when the central portion of the coin 1 coincides with the central portions of the detecting coils 5 and 7, the eddy current which is generated in the coin 1 becomes maximum and the amplitude of the detection signal S becomes minimum in accordance with the adjusting resistor R1 and the coil L1 (refer to FIG. 34D).
On the contrary, when the coin 1 is away from the detecting coils 5 and 7, in a manner similar to the case shown in FIG. 34C, the amplitude of the detection signal increases. After a time point t4 when the coin 1 is completely away from the detecting coils 5 and 7, the magnetic lines of force by the detecting coils 5 and 7 are not gradually influenced by the coin 1. The amplitude of the detection signal S finally approaches the amplitude of the output signal of the oscillating circuit 11 in a manner similar to the case shown in FIG. 34B.
On the other hand the detecting circuit regrading the detecting coil 65 also generates a detection signal S which changes in accordance with an overlap area of the detecting coil 6 and the coin 1 in a manner similar to the above case.
The detection signals S and s are analyzed and a diameter, a thickness, a material, a deforming state, and the like of the coin are judged from change patterns and minimum amplitude values of the detection signals S and s, thereby discriminating a denomination, a pseudo coin, and the like.
The detection signal S which is generated from the detecting circuit using the detecting coils 5 and 7 is a signal which is effective to judge the size, material, and thickness of the coin. The detection signal s which is generated from the detecting circuit using the detecting coil 6 is effective to judge the thickness and diameter of the coin.
However, the metal body discriminating sensors comprising the detecting coils and the metal body discriminating apparatus such as a coin detecting apparatus or the like using such sensors have the following problems.
A metal body such as a coin or the like has a structure such that the metal body moves the front surfaces of the detecting coils while rolling the guide rail. If dusts or dirts have been deposited onto the guide rail due to an installing environment of the apparatus or with the elapse of time, however, the metal body doesn't smoothly roll on the guide rail but moves while jumping. In such a case, there is a problem such that the opposite positional relation between the metal body and the detecting coils is deviated from the normal state and the detection signals are distorted and an error occurs in the discrimination. That is, the guide rail functions as a reference surface to move the metal body such as a coin or the like and there is a drawback of the principle such that when the position of the metal body is deviated from the reference surface, the measurement cannot be performed at a high accuracy.
Consequently, for instance, the maintenance to periodically clean the inside of the apparatus or the like becomes complicated and a cleaning apparatus or the like needs to be additionally provided.
Further, it is necessary to slide a coin or the like with the side wall 3 in order to smoothly move the coin or the like along the guide rail and to stabilize the distance between the coin or the like and the detecting coil under a predetermined condition by making the passing line constant when the coin or the like passes through the detecting coils. For this purpose, it is necessary to finely adjust an inclination angle of the guide rail 2 to the front side and an inclination angle of the side wall 3 to the back surface side. Since the moving characteristics of the coin or the like also change due to a difference between the material of the guide rail 2 and the material of the side wall 3, those inclination angles need to be adjusted.
There is a difference between the intensities of the magnetic lines of force which are generated from the detecting coils 5 and 7 which face each other as shown in FIG. 33 due to a difference of the opposite distance between the detecting coils 5 and 7. Therefore, an assembling accuracy of the side wall 3 and the side plate 4 need to be held constant. In addition, it is required to improve the mechanical accuracy to improve the burying accuracies of the detecting coils 5 and 7 into the side wall 3 and the side plate 4. It is, however, difficult to keep such a mechanical accuracy constant and it is necessary to frequently execute the adjustment. Particularly, since the apparatus has a structure such that if a deformed coin or the like has choked on the way of the guide rail, it is necessary to perform a procedure such that the side plate e4 is detached and, after that, the coin or like is eliminated or the like, so that there is a tendency such that the assembling accuracy of the side wall 3 and the side plate 4 gradually deteriorates. Since such a deterioration of the mechanical accuracy directly exerts an influence on the characteristics of the detection signals, the absolute measuring accuracy is low. For instance, in the case of the coin detecting apparatus to discriminate Japanese coins, the number of kinds of coins is generally set to up to four kinds. This is because an adjusting device, a differential amplifier, and a comparator are needed every denomination as will be obviously understood from FIG. 8 in JP-A-61-262990.
As mentioned above, in the case of realizing the metal body discriminating apparatus such as a coin detecting apparatus by using the conventional metal body discriminating sensors, to improve the detecting accuracy, it is extremely important to improve the mechanical accuracy of the apparatus. There are many problems to be solved such that each apparatus must be individually adjusted, the maintenance is complicated, and the like.